Device for measuring heat release in continuous calorimeter

ABSTRACT

Voltages reflecting the heat released in a continuous calorimeter and absorbed by the coolant flow therethrough are sensed and converted to a convenient parameter by means of the device described herein. The device comprises in combination an electric heater disposed to heat the coolant flow downstream of the calorimeter; means for controlling power input to the electric heater; a first and second pair of means for generating an electromotive force (EMF) as a function of temperature differential (e.g. thermocouples); means (e.g., a strip chart recorder) electrically connected to said first and second pair of generating means for comparing the voltage outputs thereof and continuously displaying the relation therebetween (or some parameter related thereto); the EMF-generating means being disposed in contact with the coolant flow and being electrically connected to the comparing and display means; the two EMFgenerating means of the first pair being disposed at the inlet and outlet, respectively, of the coolant flow to and from the calorimeter and the two EMF-generating means of the second pair being located downstream of the first pair with one upstream and one downstream of the electric heater.

United States Patent 1 Kydd et al.

[54] DEVICE FOR MEASURING HEAT RELEASE IN CONTINUOUS CALORTMETER [75]Inventors: Paul H. Kydd, Scotia; George Jernakoii, both of New York, NY.

[73 l Assignee: General Electric Company,

Schenectady. NY.

[22] Filed: Aug. 31, 1971 [21] Appl. No.: 176,475

[52] 11.8. Cl. ..73/l90 R [51] Int. Cl. ..G0lk 17/00 [58] Field ofSearch ..73/190, 193

[56] References Cited UNITED STATES PATENTS 3,589,184 6/1971 Moore73/190 2,026,179 12/1935 Keith ..73/190 2,398,606 4/1946 Wang 73/193 X3,167,957 2/1965 Ziviani .73/193 2,931,222 4/1960 Noldge et al. ..73/193POWER SUPPLY COOLANT OUTLET 40 39 COOLANT 1 Apr. 3, 1973 [57] ABSTRACTVoltages reflecting the heat released in a continuous calorimeter andabsorbed by the coolant flow therethrough are sensed and converted to aconvenient parameter by means of the device described herein. The devicecomprises in combination an electric heater disposed to heat the coolantflow downstream of the calorimeter; means for controlling power input tothe electric heater; a first and second pair of means for generating anelectromotive force (EMF) as a function of temperature differential(e.g. thermocouples); means (e.g., a strip chart recorder) electricallyconnected to said first and second pair of generating means forcomparing the voltage outputs thereof and continuously displaying therelation therebetween (or some parameter related thereto); theEMF-generating means being disposed in contact with the coolant flow andbeing electrically connected to the comparing and display means; the twoEMF- generating means of the first pair being disposed at the inlet andoutlet, respectively, of the coolant flow to and from the calorimeterand the two EMF-generating means of. the second pair being locateddownstream of the first pair with one upstream and one downstream of theelectric heater.

9 Claims, 2 Drawing Figures INLET S TR/PCH/IRT RECORDER DEVICE FORMEASURING HEAT RELEASE IN CONTINUOUS CALORIMETER BACKGROUND OF THEINVENTION The calorific value of any combustible gas measured in BritishThermal Units (BTU) is an important factor, because the chemicalpotential energy of a gaseous fuel is the principal measure of itsability to perform a given service (e.g. heating), with the exception ofthe type of application in which flame intensity is the principalcriterion. In accordance with the principle that the value of such gasis reflected in its calorific value, in many locations fuel gas ispurchased and sold on a therm (100,000 BTUs) basis. This basis of salerequires suitable equipment for accurately determining the calorificvalue (in BTU/sec or BTU/SCF) of the gas passing from the seller to theconsumer.

The water-flow calorimeter has been accepted as a standard for calorificvalue measurement by many utility companies and utility regulatingagencies. The essential parts of such commercial devices are meters forthe gas, for the combustion air and for the ambient air used for heatabsorption, a motor gear reduction unit, a water pump for the coolantwater, temperature sensing means for the entering and leaving water andfor the heated air, heat exchange means with which to cause air toabsorb the heat of combustion and recording means to measure thetemperature differences occuring in the temperature sensing devices.

Two widely recognized types of equipment for this purpose are commonlyknown as Junkers Calorimeters and Cutler-Hammer Recording Calorimeters(both employ water flow calorimetry). A considerably simplified andprecise water-flow gas calorimeter is described in U. S. Pat. No.3,589,184 Moore and the instant invention will be characterized inconnection therewith.

SUMMARY OF THE INVENTION The instant invention is a further improvementin water-flow gas calorimeter construction whereby the necessity formeasuring either the coolant flow or the temperature rise of the coolantmay be obviated. Further, fluctuations in coolant flow are notobjectionable.

In the improved construction of the instant invention the coolantcircuit for the gas calorimeter includes two pairs of identicalthermocouples (or similar means for generating electromotive force as afunction of temperature differential, e.g. thermistors, resistancethermometers), the two thermocouples of each pair of thermocouples beinglocated in contact with the coolant located at spaced first and secondstations downstreamof the coolant outlet. Electric heating means aredisposed in the system to heat the coolant flow passing between thespaced stations and means are electrically connected to the heatingmeans for controlling power input thereto. The first and second pairs ofthermocouples are electrically connected to means (eg a strip chartrecorder) for comparing the voltage outputs thereof and continuouslydisplaying the relation between these voltage outputs or some parameterrelated thereto.

Once the power input to the electric heater has been adjusted to assurea constant preselected heat release from the heater, the heating valueof the gas being supplied can be obtained as a direct and continuousreading bearing a constant relationship to the electric power input tothe heater.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of this invention aswell as other objects and advantages thereof will be readily apparentfrom consideration of the following specification relating to theannexed drawing in which:

FIG. 1 is a schematic representation of the preferred embodiment of thisinvention shown embodied in the cooling circuit of a water-flow gascalorimeter and FIG. 2 is a similar view of an alternate construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT Continuous entry of a samplingof the gas stream to be monitored into calorimeter device 10 (describedmore completely in the Moore patent, incorporated by reference) is madethrough unit 11. This unit may be a throttling device, such as acritical flow orifice meter to provide a constant sample flow rate intothe calorimeter 10 or a ratio metering device to sample in a constantproportion of the main strearmSimultaneously, air enters throughmetering valve 12 in an amount slightly in excess of the quantityrequired to completely burn the entering gas. It is necessary that thegas be metered with an accuracy at least as great as the accuracydesired in the parameter to be determined, e.g. BTU/standard cubic footor BTU/sec, while the air need not be as accurately metered and may bedetermined to an accuracy of about 5 to 10 percent. The gas andcombustion air enter closed plenum 13 via conduit 14 at ambienttemperature mixing in transit such that an air/gas mixture with a slightexcess of air is, presented to face 16 of the porous sintered metalburner plate 17, the velocity of the unburned mixture being less thanthe normal burning velocity of the particular air/ gas combination.

By way of illustration, burner 17 may be made of copper particlessintered together and defining interconnecting voids permittingcontinuous passage of the gas mixture through the sintered body 17 fromface 16 to face 21.

For this application, other metals may be employed in place of copper,for example, bronze shot, nickel shot or any structurally sound metallicshot material having a thermal conductivity at least 30 per cent of thevalue of thermal conductivity for sintered copper shot may be used bothfor the construction of burner plate 17 and also for the condenserportion of the device 10 comprising cylindrical wall 22 and bottom 23.

When the unburned gas mixture reaches face 21 (there having previouslybeen ignition at face 21 by means of spark igniter 24), it burns as aflat flame spread over face 21. The heat generated by the burningmixture is rejected in part to the burner body 17 with the burned gaseventually passing through the wall surfaces 22 and 23 leaving thedevice substantially at ambient (within'2-3C of the initial air/gastemperature) for release as flue gas.

Cooling of the combustion products to ambient temperatures isaccomplished by passing a cooling fluid through the continuous singlecopper cooling conduit 26, most of which is embedded in the sinteredmetal walls 22, 23 and in burner plate 17 for the circulation of coolingwater therethrough. In the construction shown in FIG. 1, the coolingwater (at or below room temperature, 23C) enters end 27 of conduit 26,proceeds through the length of the coiled conduit configuration embeddedin wall 22, traverses the spiral configuration embedded in base 23,passes along external leg 28 (normally insulated) to reach the flatspiral configuration embedded in burner plate 17, and exits from thecooling system via end 29 of the continuous cooling tube 26.

In this manner, the total of the heat generated during the combustion ofthe metered gas input at surface 21 is absorbed in the cooling water(with the exception of the heat in the water vapor content of theexiting gases). I-leat rejected to burner plate 17 is efficientlyremoved therefrom by the coolant circulated therein, while at the sametime the gaseous product of combustion plus any excess air pass throughwalls 22 and 23 and are cooled by the cooling water traversing coolantconduit 26 whereby the balance of the combustiongenerated heat isabsorbed.

The burner plate 17 is separate from the cup-shaped condenser (walls 22and 23) and is assembled thereto in sealed engagement by interposing asealant layer 31 (e.g. a silicone rubber gasket) th'erebetween. Removalof plate 17 to expose the cavity is facilitated by the inclusion offlexible coupling 32 in external leg 28.

The differential between the temperature of the incoming coolant and theexiting coolant generates an electromotive force across the pair ofthermocouples 33a, 33b that reflects substantially all of the heatgenerated during the combustion. As shown, the thermocouples in each ofthe thermocouple pairs are joined by an element common to eachindividual thermocouple. The thermocouples should be electricallyinsulated from the conduits in which they are mounted, if the conduitsare made of electrically conducting material.

Downstream in conduit 29 the coolant flow receives heat from electricheater 36 as the flow passes thereby. The extent to which thetemperature of the flow is raised by heater 36 in transit betweenthermocouples 37a and 37b (the second thermocouple pair) will determinethe extent of electromotive force generated thereby.

Thermocouples 37a and 37b are electrically con nected to recorder '38as, for example, to provide a reference voltage input thereto.Thermocouple 37a is shown connected to recorder 38 via amplifier 39 andresistor 40. The thermocouples 33a, 33b are electrically connected andprovide the normal input to the recorder 38.

With this arrangement calibration is easily accomplished. A gas of knownheating value is burned in calorimeter I and, simultaneously, control 41is set to adjust the power input to heater 36 to generate a voltage inthermocouple pair 37a, 3712 such as will bring about a desired readingon recorder 38, for example, a reading numerically equal to the knownheating valueof the calibration gas. Thus,.in essence, a constant ratiois established for the calibration gas between the chemical energy ofthe gasand the electrical energy provided to the electric heater. I 1

Thereafter, with this given constant power input to generate a referencevoltage input, the readout on the recorder will reflect the actualheating value (BTU/sec or BTU/SCF) of a gas flow (having thisapproximate heating value) being burned in calorimeter 10. Further, byconnecting an integrator in the system the output of recorder 38 in BTUover any given period of time can be made available to reflect totalBTUs (or therms) delivered via the main flow.

In the arrangement shown in FIG. 2 all components identified by the samenumerals are the same as in FIG. 1, however, thermocouples 33a, 33b, 37aand 37b are connected differently. Thus, the upstream thermocouples 33a,37a are interconnected electrically. Thermocouple 33b is connected toterminal 46 'of galvanometer 47 (i.e. means for sensing and comparingthe intensity and direction of current flow) and thermocouple 37b isconnected to terminal 48 thereof. Connected in this manner the voltagesapplied to galvanometer 47 are opposite in direction.

When the input of heat via heater 36 to the coolant flow is equal to thecombustion heat absorbed by the coolant, the two voltages generated inthermocouple pairs 37a, 37b and 33a, 3312 are opposite in direction andwill cancel each other producing a null reading on the galvanometer.Under this set of conditions the electric power expended (and recordedon wattmeter 49) will be identically equal (in fundamental units) to thechemical heat released in the calorimeter.

As variations in the calorific value of the sampled gas occur, thevotage from one or the other pair of thermocouples will exceed theopposing voltage. Power input to heater 36 will then be increased orreduced by the operator by resetting controller 51 so as to increase orreduce the votlage applied to terminal 48 to cancel out the voltageapplied to terminal 46. I

Thus, the total power expended and recorded on meter 49 over a period oftime, when multiplied, by an appropriate constant will be a measure ofthe chemical potential energy of the gas at constant gas sample rate orof the energy flow in a pipeline if a constant proportion of the totalflow is taken as a sample without need for measuring coolant flow,coolant temperature or temperature rise in the coolant. I

lnstad of the manual correction required in the structure of FIG. 2,this device can be made to operate automatically. Thus, thermocouples33b, 37b could be connected to a chopper (not shown) and any errorsignal passing therethrough would be amplified and used to resetcontroller 51 (as by means of a servomotor, not shown) so as to diminishand eliminate the error signal.

All water vapor from the combustion process (with the exception of thesaturation water vapor content in the exiting gases) is condensed duringpassage of the gases through walls 22 and 23 and is forced through theseporous walls to drip from the exterior thereof. The pressure drop fromdownstream of the metering means for the gas and air to the exterior ofcondenserwalls 22 and 23 is about 2 psi or less. The pressure necessaryto overcome this drop may either by supplied at the inlet to calorimeter10 or, if desired, by applying suction by means not shown to theexterior surfaces of the condenser.

The exit temperature of the burned productsis within a few degrees ofthe water temperature, so all of the heat of combustion is recovered oraccountable by a simple correction. Any excess air that accompanies theproduct also leaves at the water temperature and there is no correctionnecessary for that heat carried with it nor is there any need to meterit with extreme accuracy.

All exterior surfaces are at, or very close to, ambient temperature,therefore, virtually no heat leak corrections are required. Anycombustible gas (representing wide variations in BTU/SCF of gas) can bemonitored with only minor adjustments, if any, in gas/air flows andcontrollers 41, 51 without the need for measuring either the coolantflow or the temperature rise therein.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In a calorimeter for measuring the chemical energy content of acombustible gas wherein a combustion chamber is disposed in flowcommunication with means for effecting heat exchange between theproducts of combustion and a liquid coolant flow; means are connected tosaid heat exchange means for admitting liquid coolant flow thereto;means are connected to said heat exchange means for removing liquidcoolant flow therefrom, first and second means, respectively, areprovided for sensing the temperature of coolant flow entering andleaving said heat exchange means; said first and second sensing meansbeing electrically interconnected so that known quantities of said gascan be admitted to and burned in said combustion chamber and theresulting temperature rise in the coolant flow can be measured, thecombination with said coolant flow removing means of:

a. means for electrically heating said coolant flow located downstreamof said second sensing means;

b. means electrically connected to said heating means for adjustingelectric power input thereto at a preselected level;

c. third means for sensing the temperature of the coolant flow at alocation between said second sensing means and said heating means;

d. fourth means electrically connected to said third sensing means forsensing the temperature of the coolant flow at a location downstream ofsaid heating means and e. means electrically connected to said third andfourth sensing means and receiving a reference voltage input therefromfor comparing the voltage output of said first and second sensing meanswith said reference voltage and indicating therefrom the actual heatingvalue of the combustible gas.

2. The combination of claim 1 wherein the comparing and indicating meansis a strip chart recorder.

3. The combination of claim 1 wherein the sensing means arethermocouples.

4. The combination of claim 1 wherein the heating means is locatedwithin the means for removing coolant flow.

5. In a method for measuring the chemical energy content of acombustible gas by burning known quantities of the gas with air,effecting heat exchange between the combustion products and at least onefluid coolant flow and sensing the temperature of coolant flow enteringand leaving the heat exchanger whereby the chemical energy of thecombustion gas can be determined knowing the flow rate of the air, theadded steps of:

a. continuously introducing heat energy into the coolant flow downstreamof said heat exchanger at a predetermined rate sufficient to raise thetemperature of the coolant flow a preselected amount corresponding tothe rise in temperature of the coolant flow brought about by combustionof a gas of known calorific value,

. continuously sensing the rise in temperature in the coolant flow bythe introduction of heat energy in step a) and c. continuously comparingthe actual temperature rise in the coolant flow by heat exchange withthe preselected temperature rise in the coolant flow downstream of saidheat exchanger by the introduction of heat energy and indicatingtherefrom the actual heating value of the combustible gas.

6. The method of claim 5 wherein electric heating is employed downstreamof said heat exchanger.

7. The method of claim 6 wherein the rise in temperature of the coolantin the heat exchanger and the rise in temperature of the coolant flow byelectric heating are each determined using means for generating anelectromotive force as a function of temperature differential.

8. The method of claim 7 wherein the electromotive force-generatingmeans are thermocouples.

9. The method of claim 5 wherein the continuous comparison oftemperature rises is recorded.

1. In a calorimeter for measuring the chemical energy contEnt of acombustible gas wherein a combustion chamber is disposed in flowcommunication with means for effecting heat exchange between theproducts of combustion and a liquid coolant flow; means are connected tosaid heat exchange means for admitting liquid coolant flow thereto;means are connected to said heat exchange means for removing liquidcoolant flow therefrom, first and second means, respectively, areprovided for sensing the temperature of coolant flow entering andleaving said heat exchange means; said first and second sensing meansbeing electrically interconnected so that known quantities of said gascan be admitted to and burned in said combustion chamber and theresulting temperature rise in the coolant flow can be measured, thecombination with said coolant flow removing means of: a. means forelectrically heating said coolant flow located downstream of said secondsensing means; b. means electrically connected to said heating means foradjusting electric power input thereto at a preselected level; c. thirdmeans for sensing the temperature of the coolant flow at a locationbetween said second sensing means and said heating means; d. fourthmeans electrically connected to said third sensing means for sensing thetemperature of the coolant flow at a location downstream of said heatingmeans and e. means electrically connected to said third and fourthsensing means and receiving a reference voltage input therefrom forcomparing the voltage output of said first and second sensing means withsaid reference voltage and indicating therefrom the actual heating valueof the combustible gas.
 2. The combination of claim 1 wherein thecomparing and indicating means is a strip chart recorder.
 3. Thecombination of claim 1 wherein the sensing means are thermocouples. 4.The combination of claim 1 wherein the heating means is located withinthe means for removing coolant flow.
 5. In a method for measuring thechemical energy content of a combustible gas by burning known quantitiesof the gas with air, effecting heat exchange between the combustionproducts and at least one fluid coolant flow and sensing the temperatureof coolant flow entering and leaving the heat exchanger whereby thechemical energy of the combustion gas can be determined knowing the flowrate of the air, the added steps of: a. continuously introducing heatenergy into the coolant flow downstream of said heat exchanger at apredetermined rate sufficient to raise the temperature of the coolantflow a preselected amount corresponding to the rise in temperature ofthe coolant flow brought about by combustion of a gas of known calorificvalue, b. continuously sensing the rise in temperature in the coolantflow by the introduction of heat energy in step a) and c. continuouslycomparing the actual temperature rise in the coolant flow by heatexchange with the preselected temperature rise in the coolant flowdownstream of said heat exchanger by the introduction of heat energy andindicating therefrom the actual heating value of the combustible gas. 6.The method of claim 5 wherein electric heating is employed downstream ofsaid heat exchanger.
 7. The method of claim 6 wherein the rise intemperature of the coolant in the heat exchanger and the rise intemperature of the coolant flow by electric heating are each determinedusing means for generating an electromotive force as a function oftemperature differential.
 8. The method of claim 7 wherein theelectromotive force-generating means are thermocouples.
 9. The method ofclaim 5 wherein the continuous comparison of temperature rises isrecorded.